• 공업화학
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• 제8권2호
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• pp.191-196
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• 1997

$Pt/MoO_3/SiO_2$ 촉매계에서의 $50^{\circ}C$ 등온 환원 실험에서 hydrogen spillover는 소성 온도가 증가함에 따라 더욱 빠른 속도로 진행된다. 이는 Pt 표면위에 형성되는 overlayer에 기인하는 것임을 TEM과 CO chemisorption 측정으로 알 수 있었다. 1-butene의 iso-butene으로의 골격이성질화 반응 mechanism은 carbonium ion의 형성과 methyl기의 골격 치환의 2 step으로 알려져 있다. $Pt/MoO_3/SiO_2$ 촉매계에서 약 $250^{\circ}C$에서 calcination하면 iso-butene 수율이 증가한다. 이는 $PtCl_x$ precursor 내에 존재하는 chlorine의 감소에 의한 것과 overlayer 생성에 따라 Pt 표면으로부터 $MoO_3/SiO_2$로의 hydrogen spillover의 증가에 의한 것으로 추측된다.

• 한국재료학회지
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• 제22권10호
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• pp.531-538
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• 2012

Hollow silica spheres were prepared by spray drying of precursor solution of colloidal silica. The precursor solution is composed of 10-20 nm colloidal silica dispersed in a water or ethanol-water mixture solvent with additives of tris hydroxymethyl aminomethane. The effect of pH and concentrations of the precursor and additives on the formation of hollow sphere particles was studied. The spray drying process parameters of the precursor feeding rate, inlet temperature, and gas flow rate are controlled to produce the hollow spherical silica. The mixed solvent of ethanol and water was preferred because it improved the hollowness of the spheres better than plain water did. It was possible to obtain hollow silica from high concentration of 14.3 wt% silica precursor with pH 3. The thermal conductivity and total solar reflectivity of the hollow silica sample was measured and compared with those values of other commercial insulating fillers of glass beads and $TiO_2$ for applications of insulating paint, in which the glass beads are representative of the low thermal conductive fillers and the $TiO_2$ is representative of infrared reflective fillers. The thermal conductivity of hollow silica was comparable to that of the glass beads and the total solar reflectivity was higher than that of $TiO_2$.

• Nuclear Engineering and Technology
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• 제34권2호
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• pp.146-153
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• 2002

To radiolabel bioactive molecules, we synthesized $^{99m}$Tc-tricarbonyl precursor, [$^{99m}$Tc(CO)$_3$($H_2O$)$_3$]$^{+}$ with a low oxidation state ( I ). The [$^{99m}$Tc(CO)$_3$($H_2O$)$_3$]$^{+}$ was prepared by low pressure carbonylation (1 atm of CO) of [$^{99m}$Tc $O_4$)]$^{[-10]}$ in the presence of NaB $H_4$ resulting in higher than 98% of labeling yield and stability up to 8 hrs. We evaluated the characteristics of $^{99m}$Tc- tricarbonyl labeled bioactive molecules by carrying out in vitro and in vitro study. Prepared [$^{99m}$Tc(CO)$_3$($H_2O$)$_3$]$^{+}$ was then reacted with some ligands of significance in modem diagnostic nuclear medicine and some amino acids. Labeling yields were checked by HPLC and found to be usually high, excluding $^{99m}$Tc-tricarbonyl-MDP, -EDTMP and -mIBG. And the biodistribution properties of $^{99m}$Tc-tricarbonyl complexes applied in rabbit showed different appearance comparing with that of the $^{99m}$Tc-labeling by conventional means. From these results, we conclude that [$^{99m}$Tc(CO)$_3$($H_2O$)$_3$]$^{+}$ is a potential precursor for development of radiopharmaceuticals, especially for labeling of biomolecules.

• 한국세라믹학회지
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• 제51권5호
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• pp.477-480
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• 2014

An $Al_2O_3$-CuO-ZnO (ACZ) precursor powder was synthesized by a facial sol-gel process using a nonionic surfactant span 80 as the chelating agent to improve the surface area and morphology. When creating a hydrogen membrane, several kinds of properties are required, such as easy dissociation of hydrogen molecules, fast hydrogen diffusion, high hydrogen solubility, and resistance to hydrogen embrittlement. ACZ-Ni composite membranes (cermet) were prepared with this precursor and pure Ni powder via the hot press sintering (HPS) method. The ACZ powder was characterized by XRD, BET, and FE-SEM. Hydrogen permeation experiments were performed by Sievert's type of hydrogen permeation membrane equipment. The hydrogen permeability of ACZ/Ni 10 wt% and ACZ/Ni 20 wt% was obtained as 7.2 and $10molm^{-2}s^{-1}$ at RT, respectively. These values of the corresponding membranes were slightly increased with increasing pressures.

• 문화기술의 융합
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• 제9권3호
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• pp.587-592
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• 2023

CoCl₂·6H₂O 수용액을 결정성셀룰로오스에 함침시켜 건조한 후, 하소, 소성을 통하여 산화코발트(Co₃O₄·CoO) 초미세입자를 합성하였다. 합성된 코발트 산화물 입자의 결정구조 및 표면구조를 주사전자현미경(SEM)과 X-선회절분석(XRD)으로 조사하였다. CoCl₂·6H₂O 수용액을 함침시키는 매개체로 사용한 결정성셀룰로오스(crystalline cellulose)는 470℃ 정도에서 열분해 되었고, Co₃O₄ 결정상은 350℃에서 생성되기 시작하였다. Co₃O₄ 결정상은 500℃까지 유지되었으며, 500℃ 이상의 온도에서는 CoO 결정상으로 변화하는 것을 알 수 있었다. 열처리 온도가 증가함에 따라 산화코발트 입자의 크기가 커지는 현상이 나타났으며, 900℃ 이상의 온도에서는 입자간 용융이 일어나는 것이 관찰되었다. 하소온도 700℃ 이하의 온도에서 입자크기 2-10㎛의 Co₃O₄와 CoO의 초미세입자가 생성되는 것을 확인하였다.

• 한국분말재료학회지
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• 제27권5호
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• pp.394-400
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• 2020

Molybdenum trioxide (MoO₃) is used in various applications including sensors, photocatalysts, and batteries owing to its excellent ionic conductivity and thermal properties. It can also be used as a precursor in the hydrogen reduction process to obtain molybdenum metals. Control of the parameters governing the MoO₃ synthesis process is extremely important because the size and shape of MoO₃ in the reduction process affect the shape, size, and crystallization of Mo metal. In this study, we fabricated MoO₃ nanoparticles using a solution combustion synthesis (SCS) method that utilizes an organic additive, thereby controlling their morphology. The nucleation behavior and particle morphology were confirmed using ultraviolet-visible spectroscopy (UV-vis) and field emission scanning electron microscopy (FE-SEM). The concentration of the precursor (ammonium heptamolybdate tetrahydrate) was adjusted to be 0.1, 0.2, and 0.4 M. Depending on this concentration, different nucleation rates were obtained, thereby resulting in different particle morphologies.

• 한국자기학회지
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• 제24권2호
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• pp.51-55
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• 2014

$Fe_3O_4$ 나노입자는 hot-injection 제조법에 의해 제조되었으며 반응물질의 injection time에 변화를 주었다. 격자구조는 x-ray diffraction(XRD) 측정을 통해 Fd-3m 공간군을 갖는 cubic inverse spinel 구조로 분석되었으며, $Fe_3O_4$ 나노입자의 형상은 high-resolution transmission electron microscope(HR-TEM)으로 분석하였다. 반응물질을 각각 0.5분, 60분인 젝션시 각각 7.63 nm, 21.73 nm의 $Fe_3O_4$ 나노입자 사이즈를 얻을 수 있었다. $Fe_3O_4$ 나노입자의 자기적 특성은 다양한 온도에서 vibrating sample magnetometer(VSM)과 M$\ddot{o}$ssbauer spectroscopy로 측정하였으며, hyperthermia 측정을 통해 반응물질의 injection time이 60분일 때 50 kHz의 250 Oe에서 $Fe_3O_4$ 나노입자 파우더의 온도가 약 $120^{\circ}C$임을 관측할 수 있었다.

• Bulletin of the Korean Chemical Society
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• 제32권3호
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• pp.815-820
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• 2011

Three kinds of organometallic compounds (chromium acetylacetonate, magnesium acetate and vanadyl acetylacetonate) were used as transition metal precursor, titanium n-butoxide and multi-walled carbon nanotube as titanium and carbon precursor to prepare metal oxide-CNT/$TiO^2$ composites. The surface properties and morphology of metal oxide-CNT/$TiO^2$ composites were by Brauer-Emett-Teller (BET) surface area measurement, scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) and energy dispersive X-ray (EDX) analysis. The photocatalytic activity of prepared metal oxide-CNT/$TiO^2$ composites was determined by the degradation effect of methylene blue in an aqueous solution under irradiation of visible light.

• 한국초전도ㆍ저온공학회논문지
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• 제11권4호
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• pp.20-24
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• 2009

YBCO coated conductors (CC) on the $CeO_2$-buffered IBAD-MgO template were fabricated by metal-organic deposition (MOD) Process with Ba-trifluoroacetate and fluorine-free Y and Cu precursor materials. The precursor solution was coated on $CeO_2$-buffered IBAD MgO templates using the multiple dip-coating method, decomposed into inorganic precursors by pyrolysis up to $400^{\circ}C$ within 3 h, and finally fired at $740{\sim}800^{\circ}C$ in a reduced oxygen atmosphere. Microstructure, texture, and superconducting properties of YBCO films were found highly sensitive to both the firing temperature and time. The high critical current density ($J_C$) of $1.15\;MA/cm^2$ at 77.3K in the self-field could be obtained from $1\;{\mu}m$ thick YBCO CC, fired at $740^{\circ}C$ for 3.5 h, implying that high performance YBCO CC is producible on IBAD MgO template. Further enhancement of $J_C$ values is expected by improving the in-plane texture of $CeO_2$-buffer layer and avoiding the metal substrate contamination.

• Bulletin of the Korean Chemical Society
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• 제18권3호
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• pp.266-268
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• 1997